Various micromechanical magnetic field sensors which convert an interaction between an electrical current and the magnetic field into a force are available. German Patent No. DE 198 27 056, for example, describes a micromagnetic field sensor, in which a movement of a sensor structure induced by the Lorentz force is detected capacitively via comb-type electrodes. The Lorentz force is utilized in that a lateral movement of the free-floating structure is induced by a current, which is impressed upon an electrical conductor (free-floating) and an externally applied magnetic field.
Furthermore, there are conventional micromagnetic field sensors, which utilize the Hall effect occurring in conductors through which a current flows in the presence of an external magnetic field. Electrons in the conductors are deflected by the external magnetic field, causing a potential difference between the two ends of the conductor, constituting the Hall measurement effect. Additional measurement principles suitable for the microstructure technology include fluxgate sensors, AMR sensors and GMR sensors.
However, a sensor offset may occur in such sensors produced by the microstructure technique; this offset may occur due to tolerances or varying ambient conditions, such as temperature, atmospheric pressure or the like, necessitating an adjustment or calibration of the sensor. As part of such a calibration, a predetermined magnetic field, for example, is applied at the sensor location, and the sensor offset is calculated from the different sensor output values when the magnetic field is applied and when it is absent. German Patent No. DE 198 27 056 describes for this purpose a field coil, which is designed as a calibration current loop and is situated on the substrate surrounding the sensor. The field coil is thus integrated into the microsensor element itself. Such a configuration is also known as “coil on chip.” Since the geometric configuration of the field coil and the conductor cross section and the specific resistivity are known, the magnetic field occurring at the sensor location at a predetermined test current may be ascertained either experimentally or by calculation. The advantage in comparison with external coil configurations, which are part of a test instrument, for example, is that complex test equipment is not necessary to ensure homogeneity and stability of the field at the sensor location over time.